Program Tools

Case Study #70: Radar Trailers in Neighborhood, Bellevue, Washington

A radar trailer is a self-contained portable trailer that houses a radar unit and reader board. As a vehicle passes the trailer, the vehicle's speed is detected by the radar unit and displayed on the reader board. The idea is to bring a motorist's attention to the speed they are traveling and how it compares to the posted speed limit. With the help of its electronics staff, the city purchased and constructed its first radar trailer. The next step was to select locations throughout the city for its pilot program, which included both neighborhood streets and streets in school zones. Typical speed limits on these local and collector streets were 40 km/h (25 mi/h), or 32 km/h (20 mi/h) in the school zones.

Prior to setting out the trailer, speed studies were conducted at several sites and used as the baseline for determining the effectiveness of this new tool. Each morning, the radar trailer was placed by the Police Department's Parking Enforcement Officer and picked up each afternoon, taken back to the City for storage and battery recharging.

Two weeks following placement of the radar trailer, the Police Department conducted target speed enforcement. This approach provided residents with an opportunity to correct their driving habits and reduce their speed before enforcement began.

The initial cost of purchasing the equipment and building the radar trailer was approximately $6,000 in 1990. Since that time, the popularity of these units has increased, and manufacturers are now producing them for purchase. Today's costs range between $7,000 and $10,000, depending on the unit's features. Funds from the Neighborhood Traffic Calming Program were used to fund the project.

Results
The community response to the radar trailer pilot project was extremely positive. As evidence of this support, many residents and neighborhood groups requested radar trailers in other neighborhood locations throughout Bellevue. Over the past ten years, trailers have been used as a tool for addressing vehicle speeds in residential neighborhoods. When citizens request a trailer, they are placed on a list and are responded to on a first-come, first-serve basis. At times, this creates a backlog of up to three months for placement. To meet this high demand, the city has partnered with local tow companies to donate their time and help move the trailers around Bellevue.

In addition to their popularity, the radar trailers helped reduce vehicle speeds. Speeds were collected at several of the pilot sites before, during and after placement of the radar trailer. The results showed that vehicles traveled 5-8 km/h (3-5 mi/h) slower than before the unit was placed in-service. Several days following the placement, vehicle speeds increased slightly. However, when adding the element of enforcement vehicle speeds again decreased. Though the trailers were most effective when they were in place, yet they reduced speeds and continue to increase the safety of pedestrians traveling along and crossing streets in the neighborhoods and school zones of Bellevue.